1. Field
Example embodiments relate to thin film transistors (TFTs) and methods of manufacturing the same.
2. Description of the Related Art
Thin film transistors (TFTs) are used in various devices. For example, TFTs may be used as switching and driving devices in display devices, and as select switches in cross-point memory devices.
Amorphous silicon (a-Si) TFTs may be used as driving and switching devices in display devices. The most widely used TFTs may be a-Si TFTs, which may be uniformly formed on a large substrate with a size greater than 2 m at low cost. As display devices increase in size and quality, the performance of TFTs may be required to increase. However, there may be a limitation in using existing a-Si TFTs due to their mobility of about 0.5 cm2/Vs. Also, in general, since a-Si TFTs undergo processes at a high temperature of about 300° C., it may be difficult to apply a-Si TFTs to low temperature substrates, for example polymer substrates, for manufacturing flexible display devices.
Accordingly, various TFTs which may replace a-Si TFTs have been developed. Because polycrystalline silicon thin film transistors (poly-Si TFTs) may have high mobility on the order of tens to hundreds of cm2/Vs, poly-Si TFTs may be applied to high quality display devices in which it is difficult to apply existing a-Si TFTs. Further, poly-Si TFTs may suffer less characteristic degradation than a-Si TFTs. However, it is difficult to make poly-Si TFTs larger because of manufacturing equipment limitations and/or technical issues (e.g., poor uniformity).
It may be easy to make oxide semiconductor TFTs larger because an oxide semiconductor is amorphous. Further, oxide semiconductor TFTs have a higher mobility than a-Si TFTs. However, electrical characteristics of oxide semiconductor TFTs may change due to external factors, for example, damage, moisture and/or oxygen adsorption.
When compared with existing silicon TFTs, organic TFTs (OTFTs) may be manufactured at low cost because. An organic semiconductor layer may be formed by a wet process rather than by plasma-enhanced chemical vapour deposition (PECVD), and OTFTs may be manufactured by using a roll-to-roll process using a plastic substrate if necessary. However, OTFTs may have a lower charge mobility and a higher leakage current than silicon TFTs.